1. Field of the Invention
The present invention relates to a chemical mechanical polishing (CMP) apparatus, more particularly, to a chemical mechanical polishing apparatus with stable signals.
2. Description of the Prior Art
Currently, a chemical mechanical polishing (CMP) process is often used as a planization process in the semiconductor processing. Please refer to FIG. 1. FIG. 1 is a schematic diagram of a CMP apparatus 10 according to the prior art. The CMP apparatus 10 comprises a plurality of electric machines 12 that probably have motors and vacuum pumps for executing the CMP motion. Generally, the plurality of electric machines 12 comprises an automatic device 13 for conveying semiconductor wafers to a predetermined place, a multi-head polishing device 15 for polishing the semiconductor wafers, and a mainframe (not shown) for executing the provision of slurry and the drainage of waste water. The CMP apparatus 10 further comprises at least two control systems for controlling and coordinating the motions of the electric machines 12. As shown in FIG. 1, three control systems 14 are connected to the automatic device 13, the multi-head polishing device 15 and the mainframe respectively, wherein two adjacent control systems 14 are connected by two signal wires 16. Since the signals of the two signal wires 16 comply with RS422 communication protocol, each step in CMP process can be accurately connected with the next step.
However, in practical operation, the CMP apparatus 10 always has a breakdown or shutdown. In accordance with the information shown on a monitor (not shown), it is well known that the disconnection of the control systems 14 causes the discordance between the electric machines 12 and the shutdown of the CMP apparatus 10. Also, it will lead to over-polished semiconductor wafers and contamination on the pad and carrier during the CMP process. Furthermore, when the CMP apparatus 10 is idle, it will stop executing a wet mode and thereby dry the pad and carrier. Both of cleaning and replacing the pad and carrier are troublesome and expensive.
In order to solve the above-mentioned problems, many methods are undertaken such as changing the software on the power cord of the control systems 14, using new signal wires 16 and new terminals, adjusting the rate of transmitting the signals and exchanging a control system 14. Nevertheless, the disconnection between the control systems 14 always occurs.
The object of the present invention is a chemical mechanical polishing apparatus with stable signals to solve the above-mentioned problems.
To achieve the above-mentioned object, the chemical mechanical polishing apparatus comprises a plurality of electric machines, at least two control systems, at least two signal wires, and a wave filter. The electric machines are used to execute mechanical polishing motions. The control systems are used to control the mechanical polishing motions. The two signal wires are connected with the two control systems for transmitting signals of the two control systems, wherein the signals comply with RS422 communication protocol to coordinate the mechanical polishing motions. The wave filter comprises two terminals connected with the two signal wires respectively for filtering out the signal whose voltage exceeds a predetermined value in the two signal wires.
It is an advantage of the present invention that the chemical mechanical polishing apparatus can eliminate the noise of the two signal wires so as to provide a stable connection.
This and other objective of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.